A known orbital abrading or polishing tool includes an air-driven motor including a rotor that rotates within a motor housing inside a motor chamber. Compressed air is delivered through an inlet to the motor housing to cause rotation of the rotor. The rotor transmits rotational force to a carrier part that carries an abrading or polishing head. A key extends from the carrier part and engages a keyway in the rotor, such that rotation of the rotor causes a corresponding rotation of the carrier part and the abrading or polishing head. The polishing head can be centered about an axis that is offset from the axis of rotation of the motor, to give the polishing head an orbital movement.
Such tools often include an external body and a separate rigid motor housing piece that is inserted into the body to contain the rotor. The motor housing provides an internal surface against which the rotor rotates. The separate motor housing piece may be made of a homogeneous composition of steel or other wear-resistant material that can withstand the wear of the rotor rotating at high speed against the inner surface of the housing. The rotor can cause substantial friction against the inner surface of the housing, and thus these tools often incorporate a robust homogeneous motor housing formed from a wear-resistant material.
However, the homogeneous motor housing piece adds significant weight to the tool and is expensive to replace after extended wear. Accordingly, a need exists for an improved motor chamber for an orbital abrading or polishing tool.